I booted into Windows 7 on my boot camp partition and was about to play Dirt 3 for the 1st time.* I was in the options menu of the game and my MacBook Pro just shut down/turned off instantly. * I turned back on, holding in Option so I could boot into Windows again, but the computer just turned off immediately after the startup chime.* I turned on again, this time I didn't hold in Option, so I could boot into OS X (my default startup volume) and the same thing happened - MBP shut down immediately after the startup chime.* I tried again, same thing.* I tried again, and this time it booted fine into OS X, and all seems ok. * I tried rebooting into Windows again, and it seems fine now too. Any idea what's going on?